Posted by **Travis** on Tuesday, December 2, 2008 at 9:24pm.

Find all the solutions in the interval [0,2pi).

2sin2x - sqrt(2) = 0

sin2x = sqrt(2)/2

I'm confused by the double angle. Please help.

- Trig -
**Reiny**, Tuesday, December 2, 2008 at 9:50pm
so continue...

sin2x =√2/2

2x = 45º or 135º

x = 22.5º or x = 67.5º

in radians: x = pi/8 or 3pi/8

- Trig -
**Travis**, Tuesday, December 2, 2008 at 10:03pm
But my calculator also shows 9pi/8 and 11pi/8. Why do you have to add pi?

- Trig -
**Reiny**, Wednesday, December 3, 2008 at 8:22am
ahh, smart calculator you got there.

the period of sin2x is pi or 180 degrees

so we have to add pi to each of our answers until we are no longer in the given domain.

so x = pi/8, 3pi/8, 9pi/8 and 11pi/8

I should have taken care of that in my first post , sorry

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**lmuc odhq**, Thursday, January 1, 2009 at 1:29pm
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**hqbs xbtak**, Thursday, January 1, 2009 at 12:21pm
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